I am new to nagios, I had nagios 1.2 setup on a unix server and now trying to implement the check_snmp plugin to perform various checks on window 2000 servers. Can someone please advise where I can get a good document on the check_snmp? Especially on the paramenter object id, I am not sure what object id to use for which check. Please help.

if you use ntclient on the windows server you need to use the exact service definition as specified in the performance monitor.
Make a search in this forum for some problems about backslashes in the service names.